Field of the Invention
The field of the invention relates generally to ophthalmic lens products and more specifically to lenses and lens blanks for eyewear, in which the lenses comprise one or more photochromic materials and may comprise other agents that combine to attenuate blue light.
Description of the Related Art
Ophthalmic lenses are commonly used to correct vision errors, aberrations and focusing deficiencies caused by age, disease or other factors. In addition to correcting physiological vision problems, ophthalmic lenses and eyewear may also be used to ameliorate physical or environmental conditions (such as glare, variable lighting, high intensity light, dust, condensation, etc.) that can affect sight. Eyewear may also incorporate aesthetic features for fashion and style.
Photochromic lenses are known in the industry and are one method to address varying lighting conditions. Lenses with photochromic agents typically respond to ultraviolet (UV) light exposure (such as sunlight) by darkening to reduce visible light transmittance. They may also change color upon exposure to light. While most commonly used photochromics are activated by UV, photochromics that respond and darken when exposed to short wavelength visible light have been described, for example, in U.S. Pat. Nos. 7,320,826 B2 and 6,102,543. U.S. Pat. No. 6,926,405 B2, incorporated herein by reference, further describes lenses that respond to varying light exposures, even behind UV-attenuating windows. This is preferably accomplished by photochromics that respond to (are activated by) either or both visible and UV light; the lenses may further comprise absorbers or reflectors of visible light, polarizers and other coloring agents.
Another more recent concern is the damaging, debilitating or disruptive physical effects that may be associated with exposure to various wavelengths of visible light. Multiple and varied studies have raised concerns about the human health effects of extended or repeated exposure to blue light. Various wavelengths and spectral ranges within the blue light region have been implicated in disrupting sleep patterns and circadian rhythms, may affect blood pressure and glucose homeostasis, may reduce melatonin production (which appears to have links to depression and some higher cancer rates), and may be a contributing factor toward retinal damage, macular degeneration, cataracts and other vision problems. To complicate matters, artificial light sources, particularly the more energy-efficient LED, fluorescent, and halogen sources, and the ubiquitous backlit displays, typically have much more intense and significantly narrower (more concentrated) spectral distributions in the blue light region in comparison to the broadband sunlight to which humans have adapted over the centuries. Nonetheless, few people are willing to give up their electronic devices or curtail their normal activities to limit such exposures. Therefore, many people desire practical and unobtrusive methods to protect themselves, or at least reduce the amount of blue light exposure.
Blue-blocking lenses have been available for decades and were often prescribed following cataract and other eye surgeries. Unfortunately, because many of these lenses functioned by strongly absorbing blue light, they have a distinct and cosmetically unappealing yellow or orange tint. The pronounced blocking of blue light (often greater than 90-99% below 500 nm) also can interfere significantly with color perception, jeopardizing traffic signal recognition as well as complicating many other color-based detection systems.
Various approaches have tried to address these concerns, often by a more limited reduction of blue light exposure. For example, U.S. Pat. Nos. 5,235,358; 7,255,435 B2; 7,278,737 B2; 7,748,845 B2; 8,500,274 B2 and U. S. Application 2011/0075096 A1 describe various ways to reduce some blue light transmission or block narrower spectral portions of the blue light range of wavelengths; U.S. Pat. Nos. 8,911,082 B2; 8,770,749 B2; 5,975,695 and U.S. Application 2015/0261010 A1 describe partial reductions in multiple wavelength bands in the blue light and other visible light regions.
These varied prior attempts illustrate that neither a single nor an obvious approach to filtering or limiting blue light exposure has been universally accepted. In fact, these patents indicate that notably different techniques, different filter locations and/or combinations of filtering approaches may be required to effect better performance and desired optical and spectral results.
Thus, it is of current and considerable interest to find innovative alternatives and more advantageous approaches to blue light filtering in ophthalmic lenses.